<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>

  <button>按钮</button>
  
  <script>

    const btn = document.querySelector("button")
    btn.onclick = function() {
      console.log("btn click event")
    }

    console.log("Hello World")
    let message = "aaaa"
    message = "bbbb"

    setTimeout(() => {
      console.log("10s后的setTimeout")
    }, 0);

    console.log("Hello JavaScript")
    console.log("代码继续执行~~~")
    console.log("-------------")

  </script>

</body>
</html>